Non-Patent Literature 1 describes Application specific Congestion control for Data Communication (ACDC). ACDC is an access control mechanism for an operator to allow or prevent new access attempts from particular, operator-identified applications in a User Equipment (UE) in idle mode. Using ACDC, the operator can prevent or mitigate overload of the access network or the core network or both.
ACDC applies only to UEs in idle mode (e.g., RRC_IDLE) and does not apply to UEs in connected mode (e.g., RRC_CONNECTED). The home network (i.e., Home Public Land Mobile Network (HPLMN) or Equivalent HPLMN) is able to configure a UE with at least four ACDC categories. Each ACDC category is associated to particular, operator-identified applications, application group, or services. Provisioning of the ACDC categories in the UE is the responsibility of the home network, and the categorization is outside the scope of 3rd Generation Partnership Project (3GPP). The operator of the home network may configure the ACDC categories, for example, in the Universal Subscriber Identity Module (USIM). The operator of the home network may configure the UE with the ACDC configuration using Open Mobile Alliance Device Management (OMA-DM).
The serving network (i.e., HPLMN, Equivalent HPLMN, or Visited PLMN (VPLMN)) broadcasts control information which indicates barring information per ACDC category and also indicates whether a roaming UE shall be subject to ACDC control. The UE controls whether an access attempt for a certain application is allowed or not, based on the broadcasted barring information and the configuration of ACDC categories (i.e., mapping between the ACDC categories and the applications) in the UE.
When configuring the UE with the ACDC categories, the home network proceeds as follows. Applications whose use is expected to be restricted the least shall be assigned the highest ACDC category. Applications whose use is expected to be restricted more than applications in the highest category shall be assigned the second-to-highest ACDC category. Applications shall be assigned the third-to-highest ACDC category, and so on, in the same manner as the second-to-highest ACDC category. Applications whose use is expected to be restricted the most shall either be assigned the lowest ACDC category, or not be categorized at all.
Applications on a UE that are not assigned to any ACDC category shall be treated by the UE as part of the lowest ACDC category configured in the UE. If the operator requires differentiation with respect to these uncategorized applications, the operator should avoid assigning applications to the lowest ACDC category. When applying ACDC, the serving network broadcasts barring information starting from the highest to the lowest ACDC category.
The home network and the serving network may use different categorization. Specifically, the number of ACDC categories in the UE may not be the same as the number of ACDC categories broadcast by the serving network. This may happen, for example, when the UE is roaming and the number of categories broadcast by the serving network is different from that of the home network. In this situation, the UE proceeds as follows.
If the serving network broadcasts more ACDC categories than the UE's configuration, the UE shall use barring information for the matching ACDC categories, and shall bar uncategorized applications using the barring information for the lowest category broadcast by the serving network, and shall ignore barring information for unmatched categories.
If the serving network broadcasts barring information for fewer ACDC categories than the UE's configuration, the UE shall use barring information for the matching ACDC categories and shall bar other applications (including applications belonging to unmatched ACDC categories) using the barring information for the lowest category broadcast by the serving network.
A matching ACDC category is an ACDC category for which barring information is broadcast by the serving network and that has the same rank as the rank of a configured ACDC category in the UE. Meanwhile, an unmatched ACDC category is either an ACDC category for which barring information is broadcast by the serving network but with no corresponding ACDC category configured in the UE, or an ACDC category configured in the UE but with no corresponding barring information broadcast by the serving network.
Non-Patent Literature 2 has suggested which layer (application layer, Non-Access Stratum (NAS) layer or Radio Resource Control (RRC) layer) should perform the UE's operation required for ACDC. Specifically, Non-Patent Literature 2 has introduced some options in which the application layer, the NAS layer, or the RRC layer performs ACDC check. The ACDC check is a determination of whether to allow an access attempt triggered by an application, based on the ACDC category to which the application belongs determined by the ACDC configuration in the UE and also based on the barring information broadcasted by the serving network.
For example in the option in which the NAS layer performs the ACDC check, upon receiving a session establishment request from upper layers, if the UE is in Evolved Packet System (EPS) connection management IDLE (ECM-IDLE) mode, the NAS layer operates to:
1. Determine the ID (OS App ID) of the application triggering the request;
2. Determine to which ACDC category this OS App ID belongs based on the information provisioned to the UE by the home network operator via OMA DM or the USIM;
3. Obtain the barring information for the given ACDC category from the RRC layer;
4. Perform the ACDC check; and
5. Proceed with the Service Request procedure if the ACDC check passes.
Non-Patent Literature 2 has suggested two options in which the RRC layer performs the ACDC check. In one of the two options, upon receiving an access attempt request, if the UE is in RRC_IDLE state, the RRC layer operates to:
1. Determine the ID (OS App ID) of the application triggering the access attempt request;
2. Determine to which ACDC category this OS App ID belongs based on the information provisioned to the UE by the home network operator via OMA DM or the USIM;
3. Perform the ACDC check based on the barring information for the given ACDC category obtained from System Information Block (SIB) information; and
4. Proceed with the access attempt if the ACDC check passes.
Alternatively, in the other option in which the RRC layer performs the ACDC check, upon receiving a session establishment request, if the UE is in EMM-IDLE mode, the NAS layer operates to:
1. Determine the ID (OS App ID) of the application triggering the session establishment request;
2. determine to which ACDC category this OS App Id belongs based on the information provisioned to the UE by the home operator via Open Mobile Alliance Device Management (OMA-DM) or the USIM; and
3. Pass the corresponding ACDC category along with the Service Request and the call type to the RRC layer.
Next, upon receiving the Service Request with the call type and the ACDC category from the NAS layer, the RRC layer operates to:
1. Perform the ACDC check based on the barring information for the received ACDC category obtained from System Information Block (SIB) information; and
2. Proceed with the access attempt if the ACDC check passes.